1. We revisit here the vibration absorber introduced in Show that the solution x(t) derived from indeed verifies the mathematical model of the two-dof system at hand. Furthermore, find the natural frequencies and the modal vectors of the same two-dof system.

2. We refer here to the rotor-shaft system of Fig. 4.6a, as introduced in Investigate under which conditions θ˙ vanishes and give a physical interpretation of this case.